[Bug 1001679] New: Cyg_Counter::add_alarm() can trash list w/immediate triggers

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           Summary: Cyg_Counter::add_alarm() can trash list w/ immediate
                    triggers
           Product: eCos
           Version: 3.0
          Platform: All
        OS/Version: Other
            Status: UNCONFIRMED
          Severity: normal
          Priority: low
         Component: Kernel
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: meerjulien@gmail.com
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


Created an attachment (id=1946)
 --> (http://bugs.ecos.sourceware.org/attachment.cgi?id=1946)
Failing test case

When calling cyg_alarm_initialize with a trigger time in the past,
Cyg_Counter::add_alarm will first mark the alarm (A) as enabled before
dispatching it (B) & finally marking it as disabled (C).

Also Cyg_Counter::initialize will call rem_alarm if an alarm is enabled (D).

Hence a sequence where a callback re-enables the triggered alarm can result in
trashing the alarm list.

[begin snippet]
void Cyg_Counter::add_alarm( Cyg_Alarm *alarm )
{
    alarm->enabled = true;                     // A

    if( alarm->trigger <= counter )
    {
        alarm->alarm(alarm, alarm->data);      // B

        if( alarm->interval != 0 && alarm->enabled )
        {
            alarm->trigger += alarm->interval;
            alarm->synchronize();
        }
        else
        {
            alarm->enabled = false;            // C
            return;
        }
[end snippet]

[begin snippet]
void Cyg_Alarm::initialize(                
    cyg_tick_count    t,                // Absolute trigger time
    cyg_tick_count    i                 // Relative retrigger interval
    )
{
    Cyg_Scheduler::lock();
    if( enabled ) counter->rem_alarm(this);   // D
[end snippet]

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